Field of Invention
The present invention relates to an electronic timepiece and a control method for an electronic timepiece that adjusts the time based on signals received from positioning satellites such as GPS satellites.
Description of Related Art
The Global Positioning System (GPS) for determining the position of a GPS receiver uses GPS satellites that circle the Earth on known orbits, and each GPS satellite has an atomic clock on board. Each GPS satellite therefore keeps the time (referred to below as the GPS time or satellite time information) with extremely high precision.
An electronic device that has a timekeeping function for adjusting the time using time information (GPS time) from GPS satellites is taught, for example, in Japanese Unexamined Patent Appl. Pub. JP-A-H09-297191.
The electronic device taught in Japanese Unexamined Patent Appl. Pub. JP-A-H09-297191 receives signals from three or more GPS satellites to determine its position and the time zone at the determined position (current location). It then calculates and displays the current time at the current location using the time difference obtained for this time zone and the reference time from an internal clock.
When the electronic device taught in Japanese Unexamined Patent Appl. Pub. JP-A-H09-297191 moves to a different time zone, it can automatically adjust the change in the time difference resulting from such movement by regularly recalculating the time based on the positioning process, such as once a day.
However, the positioning process must acquire orbit information from three or more GPS satellites, the reception process is therefore time-consuming, and power consumption increases. This means that, particularly in small devices such as wristwatches where battery capacity is limited by the device size, the duration time is shortened by increased power consumption and user convenience is also impaired.